<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script type="text/javascript">
			var addStrings = function(num1, num2) {
			    let i = num1.length - 1, j = num2.length - 1, add = 0;
			    const ans = [];
			    while (i >= 0 || j >= 0 || add != 0) {
			        const x = i >= 0 ? num1.charAt(i) - '0' : 0;
			        const y = j >= 0 ? num2.charAt(j) - '0' : 0;
			        const result = x + y + add;
			        ans.push(result % 10);
			        add = Math.floor(result / 10);
			        i -= 1;
			        j -= 1;
			    }
			    return ans.reverse().join('');
			};
			console.log(addStrings("11", "1234"));
		</script>
	</body>
</html>
